It is well known fact that external energies such as heat, cold and ultrasound have long been used clinically for various medical benefits. Especially in the areas of pain management, cosmetics, healing and various therapy methods for humans or for the treatment of animals.
Thermal therapy, the application of heat and/or cold to a site of injury, is commonly recommended by Doctors/therapists for the treatment of musculoskeletal injuries. In addition, medical professionals are now prescribing simultaneous application of heat and cold energies for immediate relief of pain and inflammation caused due to injuries. It is well known that thermal therapy has benefits for both acute and chronic injuries. Procedures for application of thermal therapy in humans have been specifically defined based on tissue temperatures that have demonstrable beneficial effects. In humans, optimal therapeutic tissue temperatures range from 10° C. to 20° C. for cold therapy, and 30° C. to 45° C. for heat therapy.
Heat therapy commencing after injury results in increased local blood flow, decreased sensation of pain and increased tissue extensibility. The effects of heat therapy result in increased local tissue metabolic rate that may increase the rate of healing and facilitate stretching of local tissues.
Superficial heat is most widely used to treat patients experiencing pain, tension or hypermyotonicity because of its relaxing and palliative effects. These can heat large areas of skin/tissue but smaller volumes because the depth of penetration is less. It can raise the temperature of the tissue up to a depth of 1 cm to 2 cm. Superficial heat is used as an adjunct to an active exercise program and is most often used during the acute phases of treatment when the reduction of pain and inflammation are the primary goals.
The transfer of heat from the source to the treatment area is often classified into 3 general types: conduction, convection and radiation. An electric heat pad or hot pack shows conductive heating effects and widely used in various treatments. Normally this type of modality is applied for a time of 20 min to 30 min for devices that heat to an unknown temperature or heat to more than 40° C.
Electric heat pads have been in use for therapeutic medical purposes for many decades. Typically, a heating pad provides heat to various parts of the body for warming, pain relief and healing. In the prior art, heating pads have a square or rectangular shape and may include straps for wrapping and holding the pad around the treatment area or other areas where the heat is directed. Even heated clothing that covers a person's body has been developed for use in cold environments.
Application of cold therapy within the first 24 to 48 hr of injury results in decrease in pain, decrease in swelling, decrease in local blood flow, and decrease in the activity of inflammatory mediators at the site of injury. The typical benefits of cold therapy occurs with controlled temperatures between 10° C. to 20° C., and the benefits are immediate vasoconstriction with reflexive vasodilatation, decreased local metabolism and enzymatic activity, and decreased oxygen demand. Whereas reducing temperatures below 10° C., creates fibroblasts and microcirculations and also causes disturbances in lymphatic drainage. Cold decreases muscle spindle fiber activity and slows nerve conduction velocity, therefore it is often used to decrease spasticity and muscle guarding. The analgesic effects of cold result from a decreased nerve conduction velocity along pain fibers and a reduction of the muscle spindle activity responsible for mediating local muscle tone. It is usually most effective in the acute phase of treatment, though the patient can use it after physical therapy or the home exercise program to reduce pain and the inflammatory response.
Ultrasound energy delivery utilizes a piezoelectric material/crystal to transmit acoustic waves. Ultrasound energy when applied to the body produces a mechanical pressure wave through soft tissue to produce thermal and non-thermal effects. This pressure wave causes cell membrane distortion and generates microscopic bubbles in living tissues influencing tissue temperature, ion fluxes and intracellular activity. Cell membrane distortion also increases blood flow in and around the treatment area thus supplying fresh oxygen, nutrients, removing waste and increasing permeability of the skin, wherein the desired response in the particular tissue may greatly depend on ultrasound parameters such as frequency, intensity and time of exposure. Treatment with therapeutic ultrasound involves the method of stimulating tissue beneath the skin's surface using sound waves at 1 MHz or 3 MHz and at amplitude densities between 0.1 W/cm2 and 3 W/cm2.
When ultrasound is applied continuously, it vibrates the tissue molecules as a result of increase in kinetic energy. Tissue absorbs the produced kinetic energy and converts it to heat causing rise in tissue temperature. This also produces unstable bubbles, which collapse violently after growing to critical size under the pressure due to excessive energy accumulation. This implosion produces unstable cavities and also releases free radicals.
Ultrasound is often used as a thermal modality when treating soft tissue injuries and resultant pain; because it selectively heats structures up to 5 cm deep with only minimal increase in skin temperatures. Raising the tissue temperatures to 40° C. to 45° C. for at least 5 min using ultrasound has considerable physiological effects.
Ultrasound, when applied in pulses produces non-thermal effects and facilitates healing in the inflammatory and proliferative phase following soft tissue injury, increases local circulation because of the increased capillary density, and bone healing.
As the frequency of ultrasound increases, the attenuation (absorption, reflection and refraction of the sound) also increases. The frequency of the ultrasound waves is inversely proportional to the depth of body penetration. A 1 MHz ultrasound wave will penetrate about 3 cm to 5 cm below the skin whereas a 3 MHz ultrasound wave will only penetrate about 1 cm to 2 cm. While a low frequency means deeper penetration, using too low frequency will mean that the waves are too wide to properly move the molecules. Absorption and penetration of the ultrasound is very much dependent on collagen content of the tissue (Bone>cartilage>tendon>muscle>fat>nerve>blood).
Therapeutic ultrasound is used as a tool to improve rehabilitation, to relieve arthritis, to enhance wound healing process, to enhance drug permeation and also for cosmetic uses.
In the prior art, Kerr in U.S. Pat. No. 4,404,460 discloses a heat controlled clothing having multiple sections that are adapted to cover different areas of the human body. Electrical wires are employed which include bus wires and heater wires with circuitry controlling battery powered current flow.
Further, U.S. Pat. No. 4,736,088 issued to Bart discloses a therapeutic heating pad having a laminate structure which concentrates the flow of heat in one direction. The laminate structures in the form of a flannel material, which is held in a tubular configuration to form a muff for fomentation of a body member inserted therein.
Another specification issued to Kleshchik in U.S. Pat. No. 6,649,886 B1 discloses a highly flexible and reliable electrical heating cloth and method for providing a stable elevated temperature to an environmental site. The heating cloth consists of conductive resistive threads which are interwoven with non-conductive threads.
Another U.S. Pat. No. 5,948,012 issued to Mark V. Mahaffey discloses a cold therapy unit that includes a small portable ice chest and an electronic control unit to provide a unit which is safe to use right after surgery and has a portion which may be taken home by the patient.
Another U.S. Pat. No. 4,823,775 issued to Petrus P. M. Rindt discloses an apparatus for treating a patient with ultrasound waves comprising of a treatment head and an amplifier receiving an input signal depending on the desired intensity of the ultrasound waves and providing an electrical output signal on its output.
The devices available in the market can produce either of the energy and have their own limitations. A concern with the application of heat, especially electric heating pads, is controlling the amount of heat applied. For example, raising tissue temperatures 3° C. to 4° C. from the normal body temperature to attain physiological benefit, the source should be maintained at temperatures of 60° C. to 70° C. However prolonged exposure of high temperatures causes skin burns. The same way effective treatment with ultrasound requires use of high intensities that can not be used for longer time periods because it causes irritation and tissue damage.
In this disclosure we take advantage of these limitations and have developed a device that can produce both superficial heat and ultrasound in an efficient controlled manner to attain better physiological effect. Use of multiple energies, we believe can produce synergistic effect that is very well proven in case of ultrasound.